Other than the common cold, back pain is the number one reason people visit a doctor in the United States. There are three principle sources of back pain: i) joint pain (40%); ii) pain from a nerve root (40%); and iii) disc pain (20%). Mature and robust treatment regimens have been developed for disc and root pain including surgical, non-surgical, and epidural modalities. Effective treatment for joint pain has only emerged within the last decade, and to the present day remains elusive with only moderate success.
Spinal joint pain occurs in the facet joint between adjacent vertebrae. The five facet joints on each side of the lumbar spine produce pain signals when they become arthritic or because of injury due to trauma, with 90% of cases occurring at the L4/L5 and L5/S1 junctions. The spinal nerve root, which runs through the spinal column, innervates the vertebrae with two small medial nerve braches, called twigs. Each twig extends across a transverse process associated with each vertebral body. Nerves can have three types of fibers: motor, sensory, and autonomic. The twigs at issue are only sensory; that is, their sole function is to transmit pain via pressure, chemical, and pure pain receptors.
Consequently, cutting a medial branch of the spinal nerve root (the twig) permanently prevents it from transmitting pain signals from the joint to the brain, without compromising any motor or autonomic functionality; that is, cutting the twig stops the pain with no corresponding degradation in nerve function. Pain doctors in the medical community initially began burning the twigs with radio frequency ablation therapies, using the tip of a needle to electrocute the twig. However, radio frequency ablation therapies do not give the surgeon a very good view of the twig and, as such, the pain returned in a significant percentage of patients as twigs often grew back due to incomplete ablation.
The limited success of radio frequency ablation gave rise to the development of endoscopic attempts to more completely sever the twig, using an endoscope to bring a small camera and a light source to give the surgeon a better view of the twig during surgery. This allows the surgeon to physically cut the twig, rather than burn it through ablation, to ensure that the twig is completely severed and reduce the likelihood that the pain will subsequently return.
Presently known endoscopic techniques involve inserting a dilator into the patient, where the dilator has a radiolucent strip to allow the surgeon to locate the tip of the dilator proximate the twig under X-ray. A sheath is inserted over the dilator, and the dilator is withdrawn from the patient. An endoscope is then inserted into the sheath. Prior art endoscope cannula assemblies include 3 distinct channels: i) irrigation supply and return; ii) endoscopic probe having a camera and a slot for receiving a coagulator; and iii) a light source. Presently known endoscopic tools used for coagulating twigs at the transverse process were adapted from analogous tools developed for disc surgery, and are not well suited for use in the context of the present invention. For example, presently know endoscopic sheaths have a larger diameter than necessary to perform the function of severing the twig, and the distal tip of the sheath—having been developed for disc surgery—is not well adapted for stable placement on the transverse process.
Methods and apparatus are thus needed which overcome these and other limitations of the prior art.
Various features and characteristics will also become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background section.